The presence in spermatogenic cells of testis-specific and testis-enrighed histone variants, unique forms and levels of high mobility group proteins, and at least 5 basic nuclear proteins in late spermatids have been demonstrated by us and other laboratories. However, there is little information regarding their roles in spermatogenesis. We propose to test several hypotheses regarding their roles. First, we wish to determine whether testis-specific or -enriched histones are characteristic of primitive spermatogenic cells or whether they are associated with the commitment of spermatogonia to begin differentiation. This will be tested by isolation of pre-spermatogenic gonocytes from fetal rat testes and analysis of histones associated with them using sensitive silver staining techniques for polyacrylamide gels. Secondly, we will determine whether testis-specific or -enriched nuclear proteins are essential for meiosis in the rat by examining female meiotic cells for their presence; methods will be developed for isolating pachytene oocytes from fetal rat ovaries and nuclear proteins of these cells will be analyzed by the same methods used for gonocyte proteins. Next, we will determine specific events in nuclear protein metabolism that are associated with condensation of sperm heads. We have already shown that treatment with procarbazine can be used to procarbazine can be used to prevent condensation of the spermtidal basic protein and protamine synthesis. Temporal and dose-response information will be used to test the association between lack of condensation and abnormalities in nucleoprotein metabolism. Finally, we wish to determine the degree of involvement of nuclear proteins in the morphogenesis of the sperm head. The azh mutation in the mouse, which when homozygous results in 100% abnormal sperm heads, will be used. The levels, synthesis and modifications of nuclear proteins (both basic, non histone and nuclear matrix proteins of spermatids from azh and wild-type mice will be compared. Allophenic mice (chimeras between homozygous azh and wild type mice) will be used to test the relative importance of factors within the germ cells versus those in the Sertoli cells in shaping the sperm head. Two-dimensional gel electrophoresis will be use din an attempt to identify an altered protein of the azh gene. Since primates (including man) show many of the same testis-specific proteins as do rodents, any information obtained would be relevant to problems of human fertility and the effects of toxic agents on human spermatogenesis.